Max Tardiveau and Brian Remedios have contributed some code recently to make some CPD reports more useful. Brian has been submitting lots of excellent patches lately; one of them included some changes to the CPD Swing GUI. Now it shows a nice summary of the duplicated code results. I've uploaded a new jar file to the CPD page so you can see these changes in action via JNLP. Also, a thumbnail is below and you can click on it for a larger image:
Props to these guys for the contributions, good stuff! And if you're using PMD or CPD, consider getting the book.